**Experimental curve plotting procedure

First, data was extracted in the range of zero force from the force vs distance curve.
 Extracted data was named as dropApp1

A linear fit was made to that zero force range.
 y = P1 x +P2
	p1 = -0.64945
	p2 = -27.8480

Then, the fitted linear plot was extended unitil it meets the zero force after attraction in the force curve.
 That data was named as dropApp2

Then, baseline correction was done.
	MATLAB code used for baseline correction is named as bc in this same folder.
	MATLAB command - ycorr = bc(dropApp2(:,2),[7012,8315,9378,11061,12673],'pchip');
 	Baseline corrected data was named as ycorr.

Plot baseline corrected data.
	MATLAB command - plot(dropApp2(:,1),ycorr)

Repulsion force region was zoomed in and that data was extracted as xcorr1 and ycorr1
	plot(xcorr1,ycorr1)

To make the highest repulsion force point as zero distance,
	xcorr2 = (xcorr1-3.0546)*10^3;
	ycorr2 = ycorr1;
	plot(xcorr2,ycorr2)

**Obtaining exponential fit
This was done using MATLAB curve fitting tool.
	xdata = xcorr2
	ydata = ycorr2

General model Exp1:
     f(x) = a*exp(b*x)
Coefficients (with 95% confidence bounds):
       a =       1.322  (1.278, 1.365)
       b =    -0.03383  (-0.03545, -0.0322)

Goodness of fit:
  SSE: 5.574
  R-square: 0.9049
  Adjusted R-square: 0.9048
  RMSE: 0.09047

%plot exponential fit for the repulsive force observed
a1=1.322;
b1=-0.03383; %b1=-1/Decay length
x1=[0:0.1:350];
y1=a1*exp(b1.*x1);
plot(x1,y1,'k')

**Model vdW forces between an air bubble and a heptane droplet in water

MATLAB code

k=1.38*10^-23; %Boltzman constant
T=298; %temperature (25C)
E1=1.9; %dielectric constant of heptane
E2=1; %dielectric constant of air
E3=78.4; %dielectric constant of water
n1=1.39; %refractive index of heptane
n2=1; %refractive index of air
n3=1.33; %refractive index of water
h=6.63*10^-34; %Planck's constant
v=3*10^15; %main electronic absorption frequency
A1=(3*k*T*(E1-E3)*(E2-E3))/(4*(E1+E3)*(E2+E3));
A2=3*h*v*(n1^2-n3^2)*(n2^2-n3^2)/(8*2^0.5);
A3=(n1^2+n3^2)^0.5*+(n2^2+n3^2)^0.5*((n1^2+n3^2)^0.5+(n2^2+n3^2)^0.5);
AAirHep=A1+(A2/A3) %hamaker constant

R1=1.4*10^-6; %Radius of air bubble
R2=25*10^-6; %Radius of curvature of heptane droplet
D=[1*10^-9:0.5*10^-9:350*10^-9];
F=-(AAirHep*R1*R2)./((6*D.^2)*(R1+R2));
plot(D*10^9,F*10^9,'r')

**Model EDL forces considering highest repulsion is equal to experimental highest value
and calculated Debye length

MATLAB code

a2=1.322;
b2=-1/242; %b1=-1/Debye length
x2=[0:0.1:350];
y2=a2*exp(b2.*x2);
plot(x2,y2,'m')